Devices for long-term interface with skin can be used in after-surgical treatment, prosthetics and cosmetic piercing.
In limb prosthetics, a technology of direct skeletal attachment, called “osseointegration,” was introduced in the nineties (Eriksson and Branemark, 1994). A titanium fixture is inserted into the bone remnant of the residuum, and a skin-penetrating abutment is used for attaching the prosthesis. The surrounding skin can move freely along the device, with the formation of a layer of a pus between the skin and titanium (Haggstrom and Branemark, 2004). Despite the promising integration of a titanium implant with residual bone, the problem of the device-skin interface in the area where the implant goes outside of the residuum remains unsolved (Sullivan, Uden, Robinson et al., 2003). A study on eleven patients who have undergone this procedure in England revealed 46 episodes of superficial infection in 6 patients and a deep infection in one patient. The microbiological results were: staphylococcus aureus 33%; coagulase negative staphylococcus 7%; mixed skin flora 33%; Group A streptococci 4%; Group B streptococci 3%; alpha-haemolytic streptococcus 2%; mixed anaerobes 7%; and others 11% (Sooriakumaran, Robinson and Ward, 2004).
Attempts have been made to achieve a safer skin-device interface by using solid abutments with different roughness or covered with porous layers similar to what is suggested to improve the bone-device interface in U.S. Pat. Nos. 4,351,069; 4,756,862; 4,988,299; 5,064,425; 5,324,199; 5,405,389; 5,433,750; 5,464,440; 5,951,602; 6,582,470; 6,428,579. However, the attempts to use porously coated abutments for better skin integration were not successful (Deligianni, Katsala, Koutsoukos et al., 2001). The results of the studies (Frosch, Sondergeld, Dresing et al., 2003) indicate that porous titanium implants are biocompatible and can serve as scaffolds for surrounding bone cells. However, higher porosity is needed for the skin fibroblasts and the skin tissues. That significantly decreases the strength of the abutment, and if the abutment has only an outer coating of porous material, it can not guarantee the establishment of a reliable protection from infection.
A long-term endotracheal intubation is associated with the infections in the skin area surrounding a ventilation tube (Corner, Gibson, Weeks et al., 1976).
There is also an increasing number of reports on infections and other negative consequences of skin piercing (Hellard, Aitken, Mackintosh et al., 2003). It has been found that the wire used for piercing, even if made of titanium with thickness of 1 mm, is often surrounded by pus and the skin is inflamed (Heudorf, Kutzke and Seng, 2000).